/Engine/Source/Runtime/Engine/Classes/Engine/Engine.h
Set the custom time step that will control the Engine Framerate/Timestep. It will shutdown the previous custom time step. The new custom time step will be initialized.
the result of the custom time step initialization.
bool SetCustomTimeStep ( [UEngineCustomTimeStep](API\Runtime\Engine\Engine\UEngineCustomTimeStep) * InCustomTimeStep )